Test Cases for compose box In Mail

How to write a test case on compose box in mail?

Functional Tests	System Tests (Load Tests)
Checkout whether On clicking Compose mail, takes you to "Compose mail page"	---
Check whether it has a) To, Cc, Bcc to enter email address. b) Subject, to enter the subject of the mail c) Text body, space to enter the text.	---
Check whether a) To, Cc, Bcc accepts text. b) Subject, accepts text. c) Text body, accepts text	a) The number of email addresses that can be entered in To, Cc, and Bcc b) The maximum length of the subject c) The maxim no of words that can be entered in the text space
Check whether a) In To, Cc, Bcc, you can delete, edit, cut, copy, paste text. b) Subject, you can delete, edit, cut, copy, paste text. c) Text body, you can delete, edit, cut, copy, paste text and format text.
Check whether you can attach a file	a) The maximum size of the file that can be attached b) The max no of files that can be attached.
Check whether you can send, save or discard the mail

Performance Testing:---------------If sending mail, receiving mail etc are considered, then we could test the performance of the email server as:
1) Like if one user is connected, what is the time taken to receive a single mail.
2) If 1000s of users are connected, what is the time taken to receive the same mail.
3) If 1000s of users are connected, what is the time taken to receive a huge attachment file.

Usability Testing:-------------------
1) In Usability testing, we can check that, if a part of the email address is entered, the matching email addresses are displayed
2) If the mail is tried to send without the subject or “body of the text”, a warning is displayed.
3) If the To, Cc, Bcc contain an address, without @, it should immediately display a warning that the mail id is invalid.
4) Composing mails should be automatically stored as drafts. You can add some more testcases